1. Field of the Invention
The present invention relates to an actinic ray-sensitive or radiation-sensitive resin composition suitable for use in an ultramicrolithography process or other photofabrication process for production of very-large-scale integrated circuits or large-capacity microchips, etc. More particularly, the present invention relates to an actinic ray-sensitive or radiation-sensitive resin composition, especially a positive resist composition, suitable for use in the formation of a highly fined pattern with the use of KrF excimer laser beams, electron beams, EUV rays or the like and relates to a method of forming a pattern with the use of the composition.
In the present invention, the terms “actinic rays” and “radiation” mean, for example, radiation of the mercury lamp brightline spectrum, far ultraviolet represented by excimer laser, X-rays, electron beams or the like. In the present invention, the term “light” means actinic rays or radiation.
2. Description of the Related Art
In the production process for semiconductor devices, such as ICs and LSIs, it is conventional to perform microfabrication by lithography with the use of a photoresist composition. In recent years, the formation of an ultrafine pattern in the submicron region or quarter-micron region is increasingly demanded in accordance with the realization of high integration for integrated circuits. Accordingly, the trend of exposure wavelength toward a short wavelength, for example, from g/i rays to KrF excimer laser beams is seen.
In the lithography using KrF excimer laser beams, it is a critical issue to simultaneously satisfy all the requirements of wide exposure latitude, decrease of line edge roughness, desirable pattern configuration, excellent dry etching resistance and less defects upon development, therefore this issue needs to be resolved.
As a resist suitable for use in the lithography process using KrF excimer laser beams, electron beams or EUV rays, it is predominant to employ a chemical amplification resist utilizing an acid catalyzed reaction from the viewpoint of attainment of high sensitivity. In the field of positive resists, effective use is made of a chemical amplification resist composition composed mainly of an acid generator and a phenolic polymer with properties such that it is insoluble or poorly soluble in an alkali developer but when acted on by an acid, becomes soluble in the alkali developer (hereinafter simply referred to as “phenolic acid-decomposable resin”).
With respect to the positive resist, some resist compositions containing a phenolic acid-decomposable resin obtained by copolymerization of an acid-decomposable acrylate monomer are known. As such, there can be mentioned, for example, positive resist compositions disclosed in patent reference (1).
However, the above positive resist compositions have a drawback such that a carboxylic acid is generated at an exposed area so as to cause the dissolution rate in a developer to become extremely high, with the result that upon the actual formation of a resist pattern on a substrate, pattern upper portions become thin to thereby cause the formation of an ideal rectangular pattern to be infeasible. In order to cope with this drawback, for example, patent reference (2) proposes to employ a polymer having a repeating unit, such as methyl methacrylate or styrene, capable of reducing the polymer solubility in an alkali developer.
However, when a polymer having a repeating unit like styrene with extremely high hydrophobicity is used in a positive resist composition, the danger that the solubility in an alkali developer is excessively lowered increases, which thereby increases the probability of defects.
On the other hand, when use is made of a repeating unit like methyl methacrylate with relatively low hydrophobicity, although the development defects are less likely, the plasma etching resistance would be unsatisfactory, which would increase the difficulty of selective etching.
Furthermore, in patent reference (3), a resist composition containing a highly reactive photo-acid generator so as to attain improvement in pattern configuration and image resolution is introduced.
Despite any combination of above-mentioned technologies, it is difficult to attain balanced accomplishment of lithographic performances, and the current situation is that success has not been achieved in simultaneously satisfying of all the requirements of wide exposure latitude, decrease of LWR, desirable pattern configuration, excellent dry etching resistance and less defects upon development.    [Patent reference 1] U.S. Pat. No. 5,561,194    [Patent reference 2] JP 3116751    [Patent reference 3] Published Japanese Translation of PCT Patent Applications from Other States, 11-501909